We now need to link all of the pieces together. Starting with the left joint in fig5. we link the left inner shaft to its left inner u-joint, then the joint to the vertical pin. then the vertical pin to the dummy, then the dummy to the horizontal pin, then the horizontal pin to the left outer u-joint then from that to the left outer shaft.
Next thing that we is almost the same thing on the right side except after linking the right inner u-joint to the right horizontal pin we then link that pin to the small dummy, then the small dummy to the big one, then from there its the same again as the left setup.
the left dummy we now use a look at constraint in the rotational controller. We tell it to look at the right large dummy. The right large dummy will look at the left vertical pin (whoes rotational point is the same as the left dummy and is used since you can't have two objects looking at each other in max). It should be noted here that in getting the look at working properly sometimes your shafts might be rotated 90 degrees from its original position, don't fight with it, just rotate the other shaft. You might need to unlink something before doing this. Once this is all setup though we have reached the end of the first part which basically will allow our joints to keep together while the end shafts are animated up and down. (when i use this setup one end is attached to the gear box or transfer case and the other end goes to the rear axle which is on suspensions and will be moving up and down.) You can see the links in action in vid1.avi.
For the next part we will make the shafts rotate. Forget about using some form of dynamics setup or something we don't have time for that so we will just cheat. First off is the controlling element. Usually people use a script to control the wheels rotation on the surface. there is a car and truck plugin for max which would do the job nicely. Basically i use the wheel to control my rigs rotation. I use the wire parameters to wire the rotation on the wheel to the rotation of the outer left shaft. Due to our link the shaft will turn the outer left u-joint which will then turn the corresponding pin. Even though the dummy is linked to that pin it will not rotate since the rotation controller was changed to be a look at controller. If it did rotate then the whole thing will fall apart. We do the same thing with the right outer shaft. Now we wire the rotation on the wheel to the left inner u-joints pin. Its linking will send the rotation down into left inner shaft. On the right though i will apply the rotation of the wheel onto the small dummy since I have always gotten problems when trying to apply it to the pin. In this case the rotation of that piece was actually in the wrong direction to everyone else so i just flipped the small dummy in the x-axis (which also moved everything linked to it) then grabbed the pin and rotated it back into correct position. So now when the wheel rotates the shaft will rotate in a 1:1 ratio. if you want you can use an equation in your wiring if you don't want a 1:1 ratio. Vid2.avi will show you the rig in motion.
3DTotal
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